diff --git a/README.md b/README.md
index b9d2767..724aa0f 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@ pnpm check --fix
 To enable checks for any of the following modules, just install them:
 
 ```sh
-pnpm i -D typescript oxlint prettier publint eslint
+pnpm i -D typescript oxlint prettier publint eslint markdownlint-cli
 ```
 
 ## Contributing
@@ -30,10 +30,14 @@ bun run build
 # Run checks
 bun check --help
 bun check
+
+# Debug commands used
+DEBUG=1 bun check
 ```
 
 ### Adding Tools
 
-I've added everything I use, so if you want to add support for another tool, feel free.
-
-Just copy `src/tools/prettier.ts` and `src/tools/prettier.test.ts`, update the implementations (yes, tests are required), and add your new tool to `src/tools/index.ts`'s `ALL_TOOLS` export.
+1. Copy and rename `src/tools/prettier.ts` and `src/tools/prettier.test.ts` accordingly
+2. Implement and update tests for your new tool
+3. Add your tool to the `ALL_TOOLS` array in `src/tools/index.ts`
+4. Add the tool's NPM package to the first section of this README
diff --git a/src/tools/index.ts b/src/tools/index.ts
index 469d738..143ff3f 100644
--- a/src/tools/index.ts
+++ b/src/tools/index.ts
@@ -1,7 +1,15 @@
 import { eslint } from "./eslint";
+import { markdownlint } from "./markdownlint";
 import { oxlint } from "./oxlint";
 import { prettier } from "./prettier";
 import { publint } from "./publint";
 import { typescript } from "./typescript";
 
-export const ALL_TOOLS = [publint, prettier, typescript, oxlint, eslint];
+export const ALL_TOOLS = [
+  eslint,
+  markdownlint,
+  oxlint,
+  prettier,
+  publint,
+  typescript,
+];
diff --git a/src/tools/markdownlint.test.ts b/src/tools/markdownlint.test.ts
new file mode 100644
index 0000000..7eb2e6a
--- /dev/null
+++ b/src/tools/markdownlint.test.ts
@@ -0,0 +1,74 @@
+import { describe, it, expect } from "bun:test";
+import { parseOutput } from "./markdownlint";
+
+describe("Markdownlint", () => {
+  it("should properly parse output", async () => {
+    const stdout = "";
+    const stderr = `
+[
+  {
+    "fileName": "docs/guide/resources/upgrading.md",
+    "lineNumber": 59,
+    "ruleNames": [
+      "MD031",
+      "blanks-around-fences"
+    ],
+    "ruleDescription": "Fenced code blocks should be surrounded by blank lines",
+    "ruleInformation": "https://github.com/DavidAnson/markdownlint/blob/v0.38.0/doc/md031.md",
+    "errorDetail": null,
+    "errorContext": "\`\`\`ts",
+    "errorRange": null,
+    "fixInfo": {
+      "lineNumber": 59,
+      "insertText": "\\n"
+    }
+  },
+  {
+    "fileName": "CODE_OF_CONDUCT.md",
+    "lineNumber": 63,
+    "ruleNames": [
+      "MD034",
+      "no-bare-urls"
+    ],
+    "ruleDescription": "Bare URL used",
+    "ruleInformation": "https://github.com/DavidAnson/markdownlint/blob/v0.38.0/doc/md034.md",
+    "errorDetail": null,
+    "errorContext": "example@gmail.com",
+    "errorRange": [
+      5,
+      23
+    ],
+    "fixInfo": {
+      "editColumn": 1,
+      "deleteCount": 23,
+      "insertText": "<example@gmail.com>"
+    }
+  }
+]
+`;
+    const code = 1;
+
+    expect(parseOutput({ code, stdout, stderr })).toEqual([
+      {
+        file: "docs/guide/resources/upgrading.md",
+        message: "Fenced code blocks should be surrounded by blank lines",
+        location: {
+          line: 59,
+          column: 0,
+        },
+        rule: "MD031",
+        kind: "warning",
+      },
+      {
+        file: "CODE_OF_CONDUCT.md",
+        message: "Bare URL used",
+        location: {
+          line: 63,
+          column: 5,
+        },
+        rule: "MD034",
+        kind: "warning",
+      },
+    ]);
+  });
+});
diff --git a/src/tools/markdownlint.ts b/src/tools/markdownlint.ts
new file mode 100644
index 0000000..0741577
--- /dev/null
+++ b/src/tools/markdownlint.ts
@@ -0,0 +1,40 @@
+import type { OutputParser, ToolDefinition } from "../types";
+import { execAndParse } from "../utils";
+
+export const markdownlint: ToolDefinition = ({ root }) => {
+  const bin = "markdownlint";
+  const checkArgs = [
+    ".",
+    "--json",
+    "--ignore='**/dist/**'",
+    "--ignore='**/node_modules/**'",
+    "--ignore='**/.output/**'",
+    "--ignore='**/coverage/**'",
+  ];
+  const fixArgs = [...checkArgs, "--fix"];
+
+  return {
+    name: "Markdownlint",
+    packageName: "markdownlint-cli",
+    check: () => execAndParse(bin, checkArgs, root, parseOutput),
+    fix: () => execAndParse(bin, fixArgs, root, parseOutput),
+  };
+};
+
+export const parseOutput: OutputParser = ({ stderr: _stderr }) => {
+  const stderr = _stderr.trim();
+
+  // When there are no errors, stderr is blank
+  if (!stderr) return [];
+
+  return JSON.parse(stderr).map((warning: any) => ({
+    location: {
+      line: warning.lineNumber,
+      column: warning.errorRange?.[0] ?? 0,
+    },
+    message: warning.ruleDescription,
+    file: warning.fileName,
+    kind: "warning",
+    rule: warning.ruleNames[0],
+  }));
+};